The diffusion of health care fraud: A bipartite network analysis.

Many studies have examined the diffusion of health care innovation but less is known about the diffusion of health care fraud. In this paper, we consider the diffusion of potentially fraudulent Medicare home health care billing in the United States during 2002-16, with a focus on the 21 hospital referral regions (HRRs) covered by local Department of Justice (DOJ) anti-fraud "strike force" offices. We hypothesize that patient-sharing across home health care agencies (HHAs) provides a mechanism for the rapid diffusion of fraudulent strategies. We measure such activity using a novel bipartite mixture (or BMIX) network index, which captures patient sharing across multiple agencies and thus conveys more information about the diffusion process than conventional unipartite network measures. Using a complete population of fee-for-service Medicare claims data, we first find a remarkable increase in home health care activity between 2002 and 2009 in many regions targeted by the DOJ; average billing per Medicare enrollee in McAllen TX and Miami increased by $2127 and $2422 compared to just an average $289 increase in other HRRs not targeted by the DOJ. Second, we establish that the HRR-level BMIX (but not other network measures) was a strong predictor of above-average home health care expenditures across HRRs. Third, within HRRs, agencies sharing more patients with other agencies were predicted to increase billing. Finally, the initial 2002 BMIX index was a strong predictor of subsequent changes in HRR-level home health billing during 2002-9. These results highlight the importance of bipartite network structure in diffusion and in infection and contagion models more generally.

Use of Medicare services by elderly residents of Puerto Rico.

OBJECTIVES: We describe hospitalization rates among Medicare beneficiaries resident in Puerto Rico compared to beneficiaries in the mainland U.S., in 1999. METHODS: A cross-sectional analysis using Medicare Denominator and hospitalization files. RESULTS: The rate ratio (PR/U.S.) of age, gender-adjusted hospitalizations among elderly Medicare beneficiaries with Part A coverage was 0.78, compared with 0.92 among beneficiaries with both Part A and Part B coverage. Among the latter, the rate ratios were 0.78 for surgical admissions, 1.08 for low-variation medical conditions, and 0.97 for high variation medical conditions. They were higher for younger elderly beneficiaries. CONCLUSIONS: Rates of hospitalization in Puerto Rico may be lower, the same or exceed those of the mainland U.S. depending on the age of the beneficiary and the type of hospitalization.

Prostate biopsies in men with limited life expectancy.

CONTEXT: Authorities discourage prostate screening in men who are likely to die from causes other than prostate cancer. PRACTICE PATTERN EXAMINED: Use of prostate biopsy-a proxy for screening-in men aged 65 and older with limited life expectancy (i.e., estimated to be less than 10 years). DATA SOURCE: Five percent samples of Part A (hospital) and Part B (physician) Medicare claims for 1993 through 1997. RESULTS: 22% of all Medicare beneficiaries who underwent a prostate biopsy had a limited life expectancy, corresponding to a rate of 1420 biopsies per 100,000. This rate did not change significantly between 1993 and 1997. For men with a life expectancy greater than 10 years, the biopsy rate was 2,360 per 100,000. Among men with limited life expectancy, in the year following the biopsy, 1.6% had radical prostatectomy and 2.3% had external-beam radiation. Thirty-nine percent were hospitalized. CONCLUSION: A substantial proportion of prostate biopsies are being performed in men with a life expectancy of less than 10 years. These men are unlikely to benefit from the biopsy or subsequent treatment.